For a large portion of the United States, and particularly in the Western States, irrigation is needed for growing agricultural products as well as maintaining lawn, plants, and other landscaping around dwellings and in public areas. In 1986 there were nearly 60 million acres of agricultural land under irrigation in the United States. Of this total, nearly 40% were irrigated by sprinkler systems.
A relatively common problem in irrigation sprinkler systems is local flooding caused by missing sprinkler heads or broken risers. The result is land erosion, loss of crops, waste of water, and insufficient water to the remainder of the circuit. Currently, there is no reliable way to prevent this problem. Monitoring for failures is a major concern in operating a sprinkler irrigation system. The irrigation operators must constantly watch for missing nozzles or broken risers. Once the problem is detected, the operator must shut down the system, usually at a location removed from the break, and return to the break location to repair the nozzle or riser before the irrigation system can be re-started again. This not only demands extra labor but also causes increased operational costs and system down-time. In addition there are frequently breaks or missing nozzles that are overlooked by the operator and, left unchecked, result in serious consequences.
In most sprinkler systems, water is carried throughout the irrigation site by a water supply pipe and thence to individual sprinkler branches distributed along the pipe. In a typical system each individual sprinkler branch consists of a riser and a sprinkler head. The riser, which is a short length of vertical pipe, is connected to the supply pipe by a distribution joint, a tee or a elbow, and the sprinkler head is connected to the outlet end of the riser. The purpose of the riser is to elevate the sprinkler head to the desired level above the ground.
The sprinkler head consists of one or more small nozzles which are designed both to allow the water to exit as a stream of droplets and to limit the water flow. In the event the sprinkler head is missing or the riser is broken, the water will flow out of the affected branch at an elevated rate as a single column of water, which has the potential to cause flooding and damage the soil and the drops. In addition, the elevated flow through the damaged sprinkler branch will exhaust the overall water supply and thereby reduce the flow to the remainder sprinklers of the system. In many applications, the supply pipes, the distribution joints, and a part of the risers are installed underground, where they are reasonably well protected. However, in almost all cases, the sprinkler heads are positioned near or above the ground level and are consequently vulnerable to physical damage. The sprinkler heads are also subject to failure from vibration due to hydraulic force and mechanical fatigue.
When the sprinkler is operating normally, that is with the sprinkler head and the riser intact, the discharge flow from the sprinkler is limited by the small flow path of the sprinkler nozzle. When the sprinkler head is missing or the riser is broken, the flow restriction of the nozzle is removed. As a consequence, the outlet flow from the broken branch will drastically increase due to the reduction of flow resistance. The disclosed invention describes a method and a device that utilizes this characteristic of the drastically increased water flow to control the damaged sprinkler flow and subsequently protecting the irrigation area against the potential flooding damage.